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1 Author(s) Redacted 1 Author(s) Redacted 3 May 2011 Contrasting Growth Rates and Overall Plant Health in Brassica Rapa Utilizing Standard Fertilizer Pellets and Earthworm Castings Abstract: Brassica rapa was grown in soil fertilized by earthworm castings. Earthworm castings are advertised as an all-natural form of fertilizer that contains more nitrogen, phosphate, and other nutrients than chemical fertilizers but that will not burn a plant s roots. Pod production was compared to that of plants grown in the same soil and fertilized with standard Fast Plant fertilizer pellets. The plants fertilized with earthworm castings were found to produce fewer pods than the plants fertilized with standard fertilizer pellets. The average pod mass of the earthworm casting plants was less than that of the standard fertilizer plants. The plants also exhibited other signs of poor health such as yellow leaves and smaller size at a higher rate than the standard fertilizer plants. The data suggests that fertilizer is more effective at promoting pod growth than the earthworm castings. Introduction: Earthworms are an important contributor to healthy topsoil. After they consume organic matter, earthworms leave behind excretions known as castings < Earthworms obtain the majority of their nutrients from the bacteria and fungi within the organic matter that they consume, leaving behind their castings as a potential source of nutrients for plants (Campbell, 787). Many gardeners use earthworm castings as a source of organic nutrients for both garden and house plants. One manufacturer of earthworm castings, Wiggle Worm, claims that their castings contain five times more nitrogen (N), seven times 3- more phosphate (PO 4 ), eleven times more potash, and three times more magnesium (Mg) than ordinary topsoil, but will not burn the plants roots. The castings can be mixed into ordinary potting soil at a ratio of 1/3; one part earthworm castings for every three parts potting soil < In addition to being added directly to the topsoil, castings can also be used to create worm tea. This concoction is created by soaking earthworm castings in a gallon of water over night, straining the earthworm castings from the remaining liquid, and

2 Author(s) Redacted 2 diluting the mixture before applying it directly to the plants and surrounding soil < In previous studies on Tagetes patula plants (marigolds), the use of earthworm castings as a substrate increased the overall plant growth index, stem diameter, root growth, dry weight, and flower number (Hidalgo PR, Mata FB, and Harkess RL, Hortscience). This study examines whether using earthworm castings instead of standard fertilizer pellets increases pod formation in Brassica rapa. The study examined the effectiveness of worm castings when used as part of the substrate, as opposed to being used as worm tea or as a supplement to other fertilizers. The hypothesis was that plants grown in a substrate containing earthworm castings would grow more pods than plants grown with standard Fast Plant soil as a substrate and fertilizer pellets, due to the increased amount of nutrients delivered in way that would not burn plant roots. Materials and Methods: Two groups of sixteen Brassica rapa were planted and monitored. Group A was planted and treated according to the Carolina Fast Plant Protocols < Group B was grown according to the protocols, except that earthworm castings were added to the soil at a ratio of 1:1, and no standard fertilizer pellets were added. The plants were monitored two to three times a week, beginning the Friday after planting. Planting occurred on 1 March On 8 March, plants were trimmed to one per cell, and cells with no plants had an extra plant from a cell in the same treatment group added to them. The plants were watered daily for the first week, and two to three times weekly thereafter using a two ml plastic pipette with a squeeze bulb. One approximately full pipette was used for each plant. They were watered with tap water. Once pods began to develop, the amount of pods over 1 inch long on each plant was documented at least twice weekly. 20 days after the final pollination, the plants were removed from the water basin to dry out. After five days of drying in a drying oven, each individual pod was measured for length and weighed. The two groups were compared in the following areas: average mass of pods produced by each plant, average length of pods produced by each plant, and average number of pods produced by each plant.

Figure A: Pods Per Plant in Control Group Figure B: Pods Per Plant in Experimental Group Figure C shows the

3 Author(s) Redacted 3 Results: Figures A and B show the total number of pods for each plant on the various listed observation dates. Figure A shows pod number for Group A, while Figure B shows pod number for Group B. Figure A: Pods Per Plant in Control Group Figure B: Pods Per Plant in Experimental Group Figure C shows the average number of pods for Groups A and B on the listed observation dates. Figure C: Average Number of Pods Per Plant

Author(s) Redacted 4 According to Figure C, the control group (standard fertilizer plants) produced more pods on average on all observation dates than the treatment group (earthworm casting plants).

4 Author(s) Redacted 4 According to Figure C, the control group (standard fertilizer plants) produced more pods on average on all observation dates than the treatment group (earthworm casting plants). The final mean for the control group was pods per plant, while the final mean for the treatment group was pods per plant. As of 29 March there was only 1 plant from the control group that had not yet produced any pods over 1 inch long, while there were 4 plants in the treatment group that did not yet exhibit such pod growth. The data suggested that the use of standard fertilizer is more effective at producing higher average quantities of pods. Figure D displays the total mass of the pods produced by each plant, comparing pairs of one plant from each group. Figure D: Total Mass of Pods in Each Plant The mean pod mass for the control group was g while the mean pod mass for the treatment group was Figure E displays the average pod weight each plant. The control group exhibited a higher average pod weight in 13 of the sixteen comparisons. Figure E: Average Pod Weight of Each Plant

Author(s) Redacted 5 Figure F displays the average length of pods produced by each plant. The control group exhibited longer average pod length in 14 of the 16 comparisons.

5 Author(s) Redacted 5 Figure F displays the average length of pods produced by each plant. The control group exhibited longer average pod length in 14 of the 16 comparisons. Figure F: Average Length of Pods in Each Plant Figures D through F show that the control group tended to produce larger and healthier pods than the treatment group, as measured by both pod length and pod weight. Over the course of the observation period, many other differences between the two groups were noted that did not pertain specifically to pod growth. Some plants in each group exhibited yellow color on their leaves, and all plants needed to be staked up with wooden dowels and string for support. However, the treatment group exhibited larger numbers of yellow, brown, dry, and blotchy leaves (14 plants

6 Author(s) Redacted 6 exhibited signs of unhealthy leaves versus 11 in the control group) smaller overall size, and a larger percentage of extremely short and extremely weak plants. Discussion: The experiment conclusively disproved our hypothesis that fertilization with worm castings would be beneficial to plant growth. As shown in Figure A, the control group produced, on average, almost one pod per plant more than the treatment group. Furthermore, the control group produced only one plant with no pods over one inch, while the treatment group produced six plants with no pods. The treatment group appeared smaller in stature overall, and had a higher incidence of indicators of poor plant health such as brown and yellow leaves. Although each group had sixteen plants that grew to the flowering stage, the treatment group had the first plant that actually died. The experimental results must be viewed in light of possible sources of error. One source of error is the amount of water delivered to each plant. The water was not precisely measured, and therefore could be have been delivered in unequal amounts. There were also several occasions on which two team members mistakenly watered the plants on the same day. Receiving too much water could have a negative impact on overall plant health. Another error made in the experiment was failure to stake up the plants earlier in their development. All plants from both treatment groups ultimately required support from a stake to grow upright, and therefore receive more light. By the time they were staked, many of the plants were limp in appearance and encroaching on neighboring cells. Once they were staked, using wooden dowels and string, some plants collapsed and broke their stems. In future trials, the plants should be staked earlier in their development and plastic clips should be used instead of string to attach them to their dowels. As directed by the Carolina Fast Plant Protocols, the plants were grown in small Styrofoam cells. The two groups were grown with their sets of cells attached to each other in this experiment. It is possible the growth outcomes might have been different if either the cells were separated from each other and spread out over a larger area, or if the seeds were grown in larger containers. Once fully-grown the plants were overlapping each others space, causing smaller plants to receive reduced light. Some of the smaller plants in the treatment group may have grown larger and produced pods if they had less competition for light.

7 Author(s) Redacted 7 Although the hypothesis of this experiment was disproven, there are many other potential uses for worm castings that could be investigated in future experiments. Worm castings could be a more effective form of fertilizer if replenished at regular intervals. An experiment could test this question by adding more worm castings to the initial substrate every two weeks and then measuring growth outcomes. Another experiment could test the performance of worm castings when compared to other organic forms of fertilizer instead of the standard fertilizer used in this experiment. Finally, worm castings could be tested as a supplement to standard fertilizers, as opposed to an alternative to them. References: Fast Plants. Web. 10 February < Earthworm Castings. Web. 08 February < Worm Castings. Web. 09 February < Campbell N, Reece J, Urry L, Cain M, Wasserman S, Minorsky P, Jackson R Biology Eighth Edition. San Francisco: Pearson Benjamin Cummings p. Hidalgo P.R., Mata F.B., Harkess R.L. Physical and chemical properties of substrates containing earthworm castings and effects on marigold growth. HortScience, 41(6) pp , 2006.

Effects of Gravel on Brassica rapa

Effects of Gravel on Brassica rapa Authors' Names Redacted Abstract Brassica rapa was grown in two different groups; the control group was set up using the standard Wisconsin Fast Plant Growth instructions